The invention concerns a device according to the preliminary part of claim 1.
Such a device is known from EP 0277396. The disadvantage of the known device is that as a result of the underpressure in the milk cup the milk cup moves upwardly along the teat and can pinch the milk flow from the udder to the teat. This disadvantage arises when the leakage-air supply to the upperchamber, which is the upper part of the milk cup, is insufficiently warranted, as the teatdiameter determines how much air flows into and out of the upperchamber. One of the consequences can be that in the upperchamber the full underpressure of the milkline arises which increases the chance that the milk cup creeps upwardly which causes the teat to be pinched off.